<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style type="text/css">
        body{
            height: 600px;
        }
        .top{
            width: 100%;
            height:50%;
            background-color: #0000FF;
        }
        .left,.right{
            width: 50%;
            height: 50%;
        }
        .left{
            background-color: #3c763d;
            float: left;
        }
        .right{
            background-color: #BA2636;
            float: left;
        }
    </style>
</head>
<body>
    <div class="top"></div>
    <div class="left"></div>
    <div class="right"></div>
</body>
</html>